Fomalhaut is given the nature of Venus and Mercury, and the tradition reads it as conferring lasting fame and high honour with a spiritual or idealistic bent: and, distinctively, as being fortunate or malefic according to the conduct of the person, with blessings turning to a curse if used basely.
That conditional structure is unusual and is worth noting. Most fixed-star delineations are unconditional. Fomalhaut's makes the outcome depend on the character of the native, which is a more interesting and less falsifiable claim than the usual form.
Its inclusion among the four Royal Stars of Persia, as the Watcher of the South, is the standard modern presentation. The scheme is examined under Aldebaran and is best treated as an unsourced modern construction with a genuine astronomical intuition behind it.
Fomalhaut supplies one specific piece of evidence against the antiquity of that scheme. Agrippa's Behenian fifteen, the actual documented Renaissance list of magically significant fixed stars, includes Aldebaran, Regulus and Antares, and does not include Fomalhaut. If a four-star royal set were a live tradition available to Agrippa in 1533, its fourth member being absent from his list of fifteen is difficult to explain. Three of four appearing is what one expects if the three were independently prominent and the fourth was added later to complete a symmetry.
That is an argument from silence and should be weighted as such. It is nonetheless the kind of specific, checkable objection that is more useful than a general expression of doubt, and it points at the likeliest history: three genuinely famous stars, plus one recruited to make a set of four cardinal watchers.